Environmental protection suits are used to isolate a user from an external environment which may be hazardous or uncomfortable to a human. The environmental protection suit completely encloses a user within the suit and avoids exposure to the outside environment. The environmental protection suit may prevent exposure to an outside environment which may contain dangerous chemicals or radiation, biological contaminants, harsh environmental conditions (fire or smoke) or even uninhabitable environments (underwater, space).
The impermeable or semi-permeable garments that provide protection against hazardous environments can retain body heat that needs to be removed if the garment user is to adequately perform required tasks, especially when the user is physically active. Otherwise, trapped heat can lead to heat exhaustion or hyperthermia, a potentially dangerous condition that can severely degrade mission performance, cause injury and in extreme cases, death.
Flexible heat exchangers have proven to be one of the most effective methods of adding or extracting heat from the human body. In general, heating or cooling garments are exemplified by U.S. Pat. Nos. 3,451,812; 3,425,486; 3,419,702; 4,691,762; 4,718,429; and 4,998,415, which are incorporated herein by reference. Other types of systems for body heating and cooling are illustrated and described in U.S. Pat. Nos. 4,114,620 and 5,062,424 and Patent Publication No. 2011/0120624, each of which is incorporated herein by reference.
A liquid cooled garment (“LCG”) normally consists of a fabric shell and a labyrinth of flexible tubing affixed in some fashion to the shell. A liquid is cooled using a chiller and circulated through the LCG by a pump to which the LCG is connected through external tubing and a manifold that distributes the liquid to the LCG's tubing. Liquid chillers can be as simple as a water/ice bath or as complicated as a vapor compression refrigeration device. Whichever device is used, it lowers the temperature of the liquid below the skin temperature of the user and mechanically re-circulates the liquid through the LCG.
In many situations, the integrity of the environmental protection suit is critical to the health and safety of the wearer—the suit must remain impermeable to the hazard from which the user is being protected. However, if an LCG is to be worn underneath the suit, connections must be provided to provide an unimpeded flow path from the chiller and pump outside of the suit and the LCG inside the suit without compromising the protective barrier provided by the suit. The pass-through device must provide a durable secure connection between the interior and exterior tubing while simultaneously preventing the hazardous substance or condition, e.g., gas, fluid, radiation, heat, etc., from entering the suit.
Prior art pass-through devices are typically formed from rigid plastic such as polyamides, e.g., NYLON®. Barbs formed at inlet and outlet fittings of the pass-through device are generally used to secure the tubing. This configuration produces a significant reduction in inner diameter of the channel at the hose barbs, which impairs the performance of the garments due to the reduced liquid flow (increased back pressure) at both the input and output ports. For example, for a fitting with an inner diameter of 0.070 in. (1.78 mm) and flexible tubing having an inner diameter of 0.096 in. (2.4 mm), the barbed fitting reduces the cross-sectional area of the supply/return tubing by ˜10% to ˜50% of the garment tubing.
In addition, incompatibility in durometer (hardness) between the rigid pass-through material and the flexible PVC tubing can produce a weaker joint, requiring secondary fixation such as cable ties or clamps. On the other hand, if the same fitting configuration were to be fabricated using PVC resin, it would require a thicker cross-section to achieve strengths similar to the current rigid polymer version. Additional drawbacks of such designs include the lack of conformability to the natural curvatures and movements of the human body, which can introduce strain on the tubing due to increased flexing near the pass-through connections; increased garment wear near the location of the pass-through, and possible discomfort for the user.
Accordingly, the need remains for a pass-through device that can be used for an environmental protection suit which provides an adequate seal and an improved flow for the cooling substance.